The ornamental design for a tapecartridge for a label printer, as shown and described.
FIG. 1 is a front, top and right side perspective view of a tape cartridge for a label printer showing our new design;
FIG. 2 is a front, bottom and left side perspective view thereof;
FIG. 3 is a front view thereof;
FIG. 4 is a top plan view thereof;
FIG. 5 is a bottom plan view thereof; and,
FIG. 6 is a right side view thereof, the left side view being a mirror image of FIG. 6.
The features shown in broken lines in the drawings depict environmental subject matter only and form no part of the claimed design. The dash-dotted lines define the boundaries of the claimed design and form no part thereof.